Apple announces Family Sharing support for in-app subscriptions.
Applications could provide different subscriptions levels. For example, "shared" subscription could be offered as an upgrade to "single" one.
Build awareness with family members. You can provide custom messaging within your app depending on who purchased the subscription. Use
Apple DeveloperownershipTypeto identify whether you’re providing information to the purchaser or another family member. For example, during onboarding you might ask the purchaser to verify their Family Sharing settings as well as provide opportunities for them to share the app through a share extension.
Apple Developer: